Degradation and Characterization of Resorbable Phosphate-Based Glass Thin-Film Coatings Applied by Radio-Frequency Magnetron Sputtering

Stuart, Bryan W.; Stuart, Bryan; Gimeno-Fabra, Miquel; Segal, Joel; Ahmed, Ifty; Grant, David M.

Abstract

Quinternary phosphate-based glasses of up to 2.67 μm, deposited by radio-frequency magnetron sputtering, were degraded in distilled water and phosphate-buffered saline (PBS) to investigate their degradation characteristics. Magnetron- sputtered coatings have been structurally compared to their compositionally equivalent melt-quenched bulk glass counterparts. The coatings were found to have structurally variable surfaces to melt-quenched glass such that the respective bridging oxygen to nonbridging oxygen bonds were 34.2% to 65.8% versus 20.5% to 79.5%, forming metaphosphate (PO3)−(Q2) versus less soluble (P2O7)4− (Q1) and (PO4)3− (Q0), respectively. This factor led to highly soluble coatings, exhibiting a t1/2 degradation dependence in the first 2 h in distilled water, followed by a more characteristic linear profile because the subsequent layers were less soluble. Degradation was observed to preferentially occur, forming voids characteristic of pitting corrosion, which was confirmed by the use of a focused ion beam. Coating degradation in PBS precipitated a (PO3)−metaphosphate, an X-ray amorphous layer, which remained adherent to the substrate and seemingly formed a protective diffusion barrier, which inhibited further coating degradation. The implications are that while compositionally similar, sputter-deposited coatings and melt-quenched glasses are structurally dissimilar, most notably, with regard to the surface layer. This factor has been attributed to surface etching of the as-deposited coating layer during deposition and variation in the thermal history between the processes of magnetron sputtering and melt quenching.

Citation

Stuart, B. W., Stuart, B., Gimeno-Fabra, M., Segal, J., Ahmed, I., & Grant, D. M. (2015). Degradation and Characterization of Resorbable Phosphate-Based Glass Thin-Film Coatings Applied by Radio-Frequency Magnetron Sputtering. ACS Applied Materials and Interfaces, 7(49), 27362-27372. https://doi.org/10.1021/acsami.5b08957

• Journal Article Type: Article
• Acceptance Date: Nov 2, 2015
• Online Publication Date: Nov 2, 2015
• Publication Date: Dec 16, 2015
• Deposit Date: Jul 8, 2016
• Publicly Available Date: Jul 8, 2016
• Journal: ACS Applied Materials & Interfaces
• Print ISSN: 1944-8244
• Electronic ISSN: 1944-8252
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 7
• Issue: 49
• Pages: 27362-27372
• DOI: https://doi.org/10.1021/acsami.5b08957
• Keywords: Phosphate glass, Bioresorbable, Bioactive Thin Films, Osseointegration, Dissolution, Sputtering, PVD
• Public URL: https://nottingham-repository.worktribe.com/output/767611
• Publisher URL: http://pubs.acs.org/doi/10.1021/acsami.5b08957
• Additional Information: This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Applied Materials and Interfaces, copyright © American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/10.1021/acsami.5b08957.
• Contract Date: Jul 8, 2016